The present invention relates to an electromagnetic leakage measuring apparatus and its measuring method for measuring the power density of the leakage the electric-waves from the electronic range in the production process of electric-wave application appliances such as high-frequency heating apparatus and so on.
Generally, the power density of the leakage waves from the periphery of the door on the high-frequency heating apparatus is different in its value depending upon the size between the door inner-face shown in FIG. 1, and FIGS. 2(A) and 2(B) and the door doubling plate 2. The portion which is normally large in the gap becomes smaller. Accordingly, the pattern in the power density of the leakage waves on the entire periphery of the door of the high-frequency heating apparatus is provided in, for example, in FIG. 2(B) if the square portions of the door are A through D in FIG. 2(A).
Also, the power density of the leakage waves from the periphery of the door on the high-frequency heating apparatus momentarily changes through the rotation angle of such a wave mode converting apparatus 3 as a rotary metallic blade shown in FIG. 1. The change is repeated, with one rotation of the electric-wave agitating apparatus 3 being provided as one period, even in the same location as shown in FIG. 3. This is the same as the apparatus which is provided with such a wave mode converting apparatus as a so-called rotation antenna with the wave-feed portion being rotated at a constant period or a so-called turntable system with the food is placed and rotated. Accordingly, it is measured whether or not the power density of the leakage waves from the periphery of the door of the high-frequency heating apparatus stays within the fixed reference. Two methods shown are adapted as the measuring method to perform the deciding operation.
As shown in FIG. 4, in the first method, grasp the handle 5a of a power-density detector 5 connected with a power-density measuring apparatus 4 for portable use to get the tip end thereof closer to the periphery of the door of the high-frequency heating apparatus to seek the largest wave-leakage locations while sweeping along each side on the entire periphery of the door 6 of the high-frequency heating apparatus at a slow speed. And the same wave-leakage detector 5 is fixed to that location while the wave mode 7 of the electronic range makes at least one rotation. During this period, the maximum value of the power density to be displayed on the power density measuring apparatus 4 for portable use is read. The inspector decides whether or not the value stays within the regulated reference. Also, in the second method, the inspector of the first method sweeps the power-density detector 5 and reads the power density, and a robot and computer perform the function of judging the quality as to the power density of the leakage wave. The automatic wave-leakage measuring apparatus is shown in FIG. 5. In this method, a plurality of power density detector 8 is brought closer onto the periphery of the door of the high-frequency heating apparatus 9 by the robot to perform the sweeping operation at a slow speed in the horizontal direction or the vertical direction. The computer (not shown) detects the sweeping location of the power density detector 8 which has detected the largest value from among the power densities detected by the plurality of power density detectors 8, and its value is automatically judged, by the computer, with respect to the wave-leakage.
However, in the first method, the uniformity was removed in the measurement, deflection was caused by the inspector's dispersed operation tie, the method of measurement and so on, so that the inspection accuracy was lowered, the measurement time became uncertain so as to lower the productivity. Also, the method by the second automatic wave-leakage measuring apparatus considerably improves the defect of the first method to have large effects in the measuring accuracy improvement and the measurement time uniformity. However, such an automatic wave-leakage measuring apparatus as developed at the present time can be applied only to the measurement of the power density of the leakage waves from the high-frequency heating apparatus, which has a wave mode converting apparatus having a rotational speed of about 60 or more revolutions per minute. Namely, as shown in FIG. 6(A), when the rotational speed of the wave mode converting apparatus of the high-frequency heating apparatus is 60 revolutions or more per minute, in other words, one revolution or more per second, the period of the power density of the leakage waves by the rotation becomes one second or less, the maximum value of the power density of the leakage waves within one period is caused at the rate of one per second or less. Thus, if the power-density detector is swept at a faster speed on the door periphery of the high-frequency heating apparatus, the maximum power density by the rotation of the wave mode converting apparatus shows itself one after another in all the locations, so that the maximum value may be caught at any location. Since the time of one period is one second or less, one second or less will do when the power-density detector is secured at the maximum leakage location. As a result, it is possible to measure the power density of the leakage waves through equal-speed the sweeping operation by the power-density detector. The sweeping speed of the power-density detector in this case is performed formed at about 2.5 cm per second.
However, in recent years, the system of the wave-mode converting apparatus of the high-frequency heating apparatus is vaned. In particular, some wave-mode converting apparatuses are developed which have six revolutions per minute. The power density of the leakage waves from the electronic range which has the wave-mode converting apparatus such a slow rotational speed as described hereinabove becomes ten seconds in the period with the wave-leakage amount in the same position being momentarily changed through the rotation angle of the wave-mode converting apparatus as shown in FIG. 6(B). If the power-density detecting appliance is swept at a speed of, for example, 2.5 cm per second when the wave-mode converting apparatus is slow, the power density detector 25 cm (2.5 cm per second.times.10 seconds) is swept from the first maximum value to the next maximum value with the result that the sweeping operation has been swept without the detection of the maximum value for 25 cm. It can not be said that the measuring operation has been correctly performed. Accordingly, for the precise measurement, the sweeping speed of the power density detector is required to be made as slow as, for example, about 3 mm per second. However, the sweeping operation on the entire periphery of the door of the high-frequency heating apparatus with the sweeping speed being 3 mm per second causes a problem that the inspection time per high-frequency heating apparatus becomes very long, the productivity in the mass-production process of the high-frequency heating apparatus is considerably reduced.
When the number of power-density detectors is increased, the established interval is made shorter, and it is considered that the sweeping distance per power-density detector becomes shorter, the inspection time per electronic range becomes shorter even if the sweeping speed of the power-density detector is slow. However, when the space between the power-density detectors becomes smaller, they interfere with each other so that the power density can not be correctly detected.